My friends and I have wrestled with a determined Japanese Strike against Calcutta. My view as to the best countermeasure is to buttress the UK with Australian and American air units. The US has a fighter and TAC in Hawaii that can be in Queensland by US1 and in Java by US2. Similarly, some or all of the Anzac fighters can reach there by AU2.
The UK can protect Java by transporting a couple of infantry there on UK1. Then possibly putting up a screen of the island with its surface ships on UK2 if there is an opportunity. If not used for a screen, then navy should turtle to the Indian sea zone to protect against an amphibeous assault. An all out defense of Malaya doesn’t seem fruitful as it is vulnerable to massive air strikes as early as J2. Any air units diverted there will be lost rapidly.
If the US and ANZAC can get 4 or 5 fighters and TACs to Burma/India by turn 3 or 4, the UK should be able to bog down a Japanese attack.
For the UK, buying inf and art is probably the best option as there will be a premium on defense value early on. The UK should have enough resources to trade Shan state for a couple turns. Move the AA gun to Burma - it will be of more use there to defend against an overland attack. That should buy some time. Of course, by the end of J3, the UK’s economic power will be severely curtailed.
China plays a critical role. China must keep the Burma road open to keep its build capacity alive. Probably means constructing an artillery each turn bolster attack strength retaking Yunan from Schechwan.
Apart from the US “loan” of air to British, there may be an opportunity to take the Caroline islands. A japanese all out rush for India will leave them vulnerable elsewhere. Caroline is a more effective way to project US force than Wake. It already has a naval base and projects US naval and air strength to a larger share of the relevant board. From there, it may be possible to take back the PI or shift major strength to Guam. The Japanese would have to divert attention to counter either of these moves as their transports and/or asian ICs would be vulnerable.
Just some food for thought.